1. Field of the Invention
The present invention relates to a planar light source apparatus used in a liquid-crystal display apparatus or the like, and to a lens film that is suitable for used in such as planar light source apparatus.
2. Description of the Related Art
As shown in FIG. 7, for example, for edge lighting, a planar light source apparatus 2 in a transmission-type liquid-crystal display apparatus 1 of the past is formed by a light source lamp 3 and light-transmitting material that is approximately planar in form, this light source having a light guide 4, which receives incident light that is emitted from the light source lamp 3 at one edge surface 4A and emits this light from a light exiting surface 4B.
In the Japanese Unexamined Patent Application publication H4-107201, there is the disclosure of such a planar light source apparatus, this apparatus having a lens film 6 that has a plurality of unit lenses 6A that are arranged with a prescribed pitch in either one direction or directions in two dimensions, this being disposed on the light exiting surface 4B side of the above-noted light guide 4, with a light-diffusing sheet 5 between the lens film 6 and the light guide 4.
In the liquid-crystal panel 7 that is illuminated by the above-noted planar light source apparatus 2 is configured so that the two surfaces of the liquid-crystal cell 7 are held between the polarizers 9A and 9B. The reference numeral 8 in FIG. 7 denotes a reflective sheet for the purpose of reflecting light that exits from the rear surface of the light guide 4 so that the light is returned to the light guide 4, and 4D denotes a light-scattering element.
The lens film 6 is usually positioned so that the ends of the unit lenses 6A of the lens film 6 make physical contact with the polarizer 9B or make contact with the light exiting surface 4B of the light guide 4.
However, because the ends of the above-noted unit lenses are usually pointed, with an angle in the area of 90.degree., there is the problem of a susceptibility to damage to the polarizer 9B or light exiting surface 4B of the light guide 4 with which they come in contact. In the case in which two lens films are overlaid in the same direction, there is a tendency for damage to occur in the flat part.
If the unit lenses 6A are made of a soft material, so as to avoid damaging the polarizer 9B or the light exiting surface 4B of the light guide 4, there is a tendency for them to deform by the action of the contact force, thereby leading to the new problem of it being impossible to maintain the performance of the lenses.
If the pitch of the unit lenses 6A is made large, there is a reduction in the number of unit lenses that make contact with the polarizer 9B or the light exiting surface 4B, this causing an increase in the load that each unit lens 6A bears, leading to a tendency of the polarizer 9B or light exiting surface 4B being damaged by stress concentrations. In contrast to this, if the shape of the past is used, there is the problem of a tendency for the lenses themselves to be damaged.